I think they will be very stiff,no real way to measure unless you make a smaller spine tester.For weight up front,thats a tough question.Depends on the bow,if it is a longbow not cut to center I don't think you could add enough weight.A stiff arrow like the will deflect on the riser and not flex around it.I had some carbons the were cut just past my draw length and they were showing stiff.So I tried adding more weight up front and the worse they go,they were bouncing off the riser and not flexing around it,this was an off center cut longbow.What I did when stiff arrows from my whell bow days was to make them into flu flu's.I think they will be really stiff for a youth.